add DocumentLink support

[srivastava-diya]

Description

Adds documentLink support, scoped to what this language server actually owns, the document's own $schema declaration.

• If a JSON document's top-level $schema value resolves to a schema file inside an open workspace folder, that value becomes a clickable link to the schema file.

• Links are not created for $schema values that resolve to a SchemaStore.org URL (or any non-workspace location).

• Workspace folder URIs are normalized before comparison against the resolved $schema URI, since VS Code sends them with a %3A that doesn't match the unencoded form produced when resolving $schema.

[srivastava-diya]

I thought of using @hyperjump/browser's get() as the primary resolution mechanism, I used this same approach for my JRef Qualification task, but it turns out not to be effective here. SchemaStore already owns the single global application/json media-type, so get() gives back schema-compiler internals, not the plain JSON content of the file. I confirmed this by using step() on a .json file which returned {}

Registering a second application/json plugin isn't an option either.

Given all that, i added manual resolution.

[jdesrosiers]

I consider this to be out of scope. This is a language server for JSON files. It uses JSON Schema, for validating JSON, but it's not intended to be a language server for editing JSON Schema files. It should treat JSON Schema files as plain JSON files, which means it doesn't know that $ref is a link. It should be treated as just a string. DocumentLinks for $ref is for the JSON Schema language server to implement.

The only thing we should be creating document links for in this language server is $schema. If $schema points to a schema in the workspace (rather than from SchemaStore.org), we can make it clickable.

[srivastava-diya]

The only thing we should be creating document links for in this language server is $schema. If $schema points to a schema in the workspace (rather than from SchemaStore.org), we can make it clickable.

sure and my bad for not thinking through this before, i'll change the implementation accordingly.

[srivastava-diya]

Added a custom tooltip so that user will know that this specific link opens the associated schema, because the default tooltip text ("Follow link") is generic and opens any external link, so this distinguishes our link from theirs.